How does "Flip Normals" affect Face Corner Data?
I would assume this is due to the fact that it is a bunch of disconnected planes which are treated like one object. In the newer Blender 2.8x+ series, normals are automatically corrected while editing in edit mode.
The problem in your case is that all of the disconnected planes are being treated as if they are one object, and therefore, the normals are going to look very messed up. However, if you try this with all the planes connected into a full, closed mesh, you should see this problem disappear when you recalculate (if needed) the normals. If you flip the normals, they should flip.